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electrical_engineering_and_electronics_1:block03 [2025/10/10 21:40] – [Preparation at Home] mexleadminelectrical_engineering_and_electronics_1:block03 [2026/01/10 13:27] (aktuell) – mexleadmin
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-====== Block 03 — Electric resistance and power ======+====== Block 03 — Electric Resistance and Power ======
  
-===== Learning objectives =====+===== 3.0 Intro ===== 
 + 
 +==== 3.0.1 Learning Objectives ====
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 After this 90-minute block, you can After this 90-minute block, you can
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-===== Preparation at Home =====+==== 3.0.2 Preparation at Home ====
  
 Well, again  Well, again 
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   * 1.7.2   * 1.7.2
  
-===== 90-minute plan =====+==== 3.0.3 90-minute plan ====
   - Warm-up (8 min):    - Warm-up (8 min): 
     - recall charge, current, voltage     - recall charge, current, voltage
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   - Wrap-up (5 min): Summary box; common pitfalls checklist.   - Wrap-up (5 min): Summary box; common pitfalls checklist.
  
-===== Conceptual overview =====+==== 3.0.4 Conceptual Overview ====
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   - **Power** is the rate of energy conversion: $P=\dfrac{\rm dW}{\rm dt}$. In DC, $W=U\cdot I\cdot t$ and $P=U\cdot I$.   - **Power** is the rate of energy conversion: $P=\dfrac{\rm dW}{\rm dt}$. In DC, $W=U\cdot I\cdot t$ and $P=U\cdot I$.
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-===== Core content =====+===== 3.1 Core Content =====
  
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 These elements will be considered in more detail below. These elements will be considered in more detail below.
  
-==== Consumer ====+==== 3.1.1 Consumer ====
  
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-==== Ohmic resistance ====+==== 3.1.2 Ohmic resistance ====
  
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-==== Linearity of Resistors ====+==== 3.1.3 Linearity of Resistors ====
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-==== Ideal sources ====+==== 3.1.4 Ideal Sources ====
   * Sources act as generators of electrical energy   * Sources act as generators of electrical energy
   * A distinction is made between ideal and real sources. \\ The real sources are described in the following chapter "[[Block06]]".   * A distinction is made between ideal and real sources. \\ The real sources are described in the following chapter "[[Block06]]".
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   * The specific conductance $\kappa$ is the reciprocal of the specific resistance $\rho$: \\ $\kappa={{1}\over{\rho}}$   * The specific conductance $\kappa$ is the reciprocal of the specific resistance $\rho$: \\ $\kappa={{1}\over{\rho}}$
  
-==== Conductivity of Matter ====+==== 3.1.5 Conductivity of Matter ====
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-==== Temperature dependence of resistance ====+==== 3.1.6 Temperature Dependence of Resistance ====
  
 The resistance value is - apart from the influences of geometry and material mentioned so far - also influenced by other effects. These are e.g.: The resistance value is - apart from the influences of geometry and material mentioned so far - also influenced by other effects. These are e.g.:
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-==== Power and energy ====+==== 3.1.7 Power and Energy ====
  
 We know that a movement of a charge across a potential difference corresponds to a change in energy.  We know that a movement of a charge across a potential difference corresponds to a change in energy. 
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-==== Passive vs. active sign convention ====+==== 3.1.8 Passive vs. Active Sign Convention ====
    
 For **loads** (passive convention): current enters the $+$ terminal; $P=U\cdot I>0$ → absorption.   For **loads** (passive convention): current enters the $+$ terminal; $P=U\cdot I>0$ → absorption.  
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-===== Common pitfalls =====+===== 3.2 Common Pitfalls =====
   * Don’t mix conventions: use **passive** for loads when computing $P=U\cdot I$ as absorbed power.   * Don’t mix conventions: use **passive** for loads when computing $P=U\cdot I$ as absorbed power.
   * Always attach **units** (e.g., $I=2~{\rm A}$). Check $P$ with **two forms** ($R I^2$ vs. $U^2/R$) to catch arithmetic slips.   * Always attach **units** (e.g., $I=2~{\rm A}$). Check $P$ with **two forms** ($R I^2$ vs. $U^2/R$) to catch arithmetic slips.
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   * Temperature law is **approximate** near the reference (often $20^\circ\rm C$); large $\Delta T$ or semiconductors need better models.   * Temperature law is **approximate** near the reference (often $20^\circ\rm C$); large $\Delta T$ or semiconductors need better models.
  
-===== Exercises =====+===== 3.3 Exercises =====
 ==== Worked examples ==== ==== Worked examples ====
  
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 Which wire cross-section $A_{\rm Cu}$ must be selected? Which wire cross-section $A_{\rm Cu}$ must be selected?
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